This invention relates to bending brakes and more particularly to the means for retaining and locking the working tools used by these brakes.
Bending brakes generally comprise a structure supporting two vertically-positioned substantially coplanar opposing toolplates, of which one can move vertically.
To the facing edges of the toolplates are fixed the means for retaining and locking the punch and die respectively, each of these being formed from a plurality of tools aligned in succession, they having the same shape but different lengths.
The modular means for retaining and locking the tool are fixed to the respective toolplates by known means, and are arranged to receive the tool shank in a manner enabling it to be slid along an axis parallel to the toolplate edge and be locked in the desired position.
When the type of work changes, one or more tools have also to be changed, this being generally done by withdrawing or inserting the tools laterally from or into the respective retention and locking means in the direction of the edge of the metal sheet.
Withdrawing, adding or changing a tool is a particularly delicate and even dangerous operation, particularly with regard to the upper tools, which can also be very long and heavy.
For this reason, tool retention and locking means have been developed for bending brakes which enable the tool to be withdrawn vertically, in the brake working direction.
These known means are rather complicated because they have to utilize safety means to prevent the tool from falling down when it is released.
Equipment known in the art, comprising said tool retention and locking means, is fully described in EP 0494714, in which the tool retention and locking means includes a lower channel into which the upper portion of the tool, also known as the shank, is inserted.
The tool can be inserted from below into a seat having the same form as the shank, and locked in position by a plurality of pneumatically operated pistons which enter a longitudinal groove provided in the tool shank. Each of these devices also has a safety device which includes a lever-operated peg which is movable within a hole in the retention means so that when the shank has been inserted into the seat in the retention and locking means, is maintained elastically inserted in a longitudinal cavity provided in one of the vertical walls of the seat.
At this point the tool can be withdrawn in the direction of the sheet edge or, by pressing the lever, can be withdrawn in the vertical direction.
This solution is costly to implement, and in addition the peg present in the safety device is easily damaged during use, rendering it unable to perform its safety function.
An object of the invention is to overcome the aforementioned drawbacks within the framework of a rational, reliable and low-cost solution.
A further object of the invention is to provide tool retention and locking means which can be used easily and safely by the operator.